Work feeding mechanism for automatic machine tools



Sept. 18, 1956 w. E. R. PULMAN 2,763,365

WORK FEEDING MECHANISM FOR AUTOMATIC MACHINE TOOLS Filed May 19, 1952 5 Sheets-Sheet 1 [ave/Zia}- William flia-s fieyl'na [cl Pal/nan Sept. 18, 1956 w. E. R. PULMAN 2,763,365

WORK FEEDING MECHANISM FOR AUTOMATIC MACHINE TOOLS Filed may 19, 1952 5 Sheet-Sheet 2 vi fin enzar Mlliam Elias Feye'nald Phlman Sept. 18, 1956 w. E. R. PULMAN 2,763,365

WORK FEEDING MECHANISM FOR AUTOMATIC MACHINE TOOLS Filed May 19, 1952 5 Sheets-Sheet 3 llll flfol' Ml! [am Eli as Reginald Rd: :zn

Sept. 18, 1956 t w. E. R. PULMAN 2,763,365

WORK FEEDING MECHANISM FOR AUTOMATIC MACHINE TOOLS Filed May 19, 1952 5 Sheets-Sheet 4 William 11 ,9 4?? young 7 4 7M Sept. 18, 1956 W.'E. R. PULMAN 2,763,365

WORK FEEDING MECHANISM FOR AUTOMATIC MACHINE TOOLS Filed May 19, 1952 5 Sheets-Sheet 5 Fya.

I l I I In men for William 11214- )?eyin a/JPalmam United States Patent WORK FEEDING MECHANISM FOR AUTOMATIC MACHINE TOOLS William Elias Reginald Pulman, 'Hov'e, England, assignor to- C. V. A. Jigs, Moulds & Tools Limited, Hove, England, a British company Application May 19, 1952, SerialNo. 288,587

Claims priority, application Great Britain May 18, 1951 Claims. (Cl. 203-150) This invention relates to work feeding mechanism for automatic machine tools and particularly for automatic turret lathes in which the work is fed through a hollow work spindle between the jaws of a collet or chuck. The object of the invention is to prevent damage occurring should the work jam during feeding.

According to this invention a work feeding mechanism for automatic machine tools comprises a reciprocabl-y or osc'illatably mounted operating member connected to an element which engages the work, means for imparting reciprocation or oscillation to said operating member and resilient means arranged to resist the driving reaction but to yield at a predetermined load.

The aforesaid operating member may comprise a lever arm having a pivotal mounting and there are provided means connecting said lever arm to the element which engages the work, means operating upon said lever arm so as to oscillate itand loaded resilient means operating on said pivotal mounting in a direction which opposes the driving reaction.

The aforesaid pivot-a l mounting may be carried by a second lever arm mounted to swing about a fixed axis and the aforesaid loaded resilient means may be connected to either lever arm or to the pivotal mounting between them so as to urge the'second lever arm against a stop. The aforesaid loaded resilient means may comprise a tension spring.

The pivotal mounting between the two lever arms may be arranged to be adjustable along the lengths thereof whereby the extent of the feeding motion for the work may be adjusted. The means for adjusting the position of the pivotal mounting may be associated with the first :said lever arm "and a part of the pivotal mounting may be free to move along a slot in the first lever arm and a projection or like on said lever arm disposed away from the pivotal mounting is constrained to move rectilinearly in a direction "transverse to the direction of movement of the pivotal mounting along said arms.

The first said lever arm is arranged to be oscillated .by a barrel cam, a groove in which is engaged by a cam follower on the end of said lever arm while a projection :on said arm is arranged to engage a :guide slot parallel with the axis of rotation of the barrel cam whereby the point of engagement between the lever arm and the barrel learn is prevented from moving transversely to the axis of rotation as the lever arm oscillates; With the above arrangement the aforesaid .pivotal mounting between the two lever arms is held stationary by reason of the tension in the spring swinging the second lever arm about the aforesaid fixed axis and maintaining it in engagement with a stop. Should however the element which engages the work be arrested the pivotal mounting between the two arms will overcome the tension in the spring and the first said lever arm will then swing about the point of connection of its end with the element which feeds the work.

The following is a more detailed description of the invention as applied to an automatic turret lathe.

Reference being made to the accompanying drawings in which:

Figure 1 is a vertical section through. one part of the headstock of the lathe showing the work spindle and feed tube,

Figure 2 is a section through another part. of the headstock of the lathe, looking from. the opposite side to that of Figure 1,

Figure 3 is a sectional end elevation looking from the right of Figure 2 and showing the operating mechanism for imparting reciprocable movement to the feed tube,

Figure 4 is a side elevation of the part of the mechanism shown in Figure 2, and of the operating mechanism, and

Figure 5 is a plan view of the arrangement shown in Figure 3.

The turret lathe is provided in known manner with a hollow work spindle 10 (see Figure 1) having a collet 11 mounted at one end and having a reciprocable feed tube 12 (see Figure 2') extending into the spindle and provided with gripping fingers 13 for engaging the work which passes along said tube. The tube has rotatably mounted upon it an outer sleeve 14 having an external circumferential groove 15 which is engaged by a plate 16 which is hinged to a fixed outermost sleeve 17 encircling the assemblage and is maintained in engagement by a suitable latch 45 (see Figure 3) which engages a flange integral with the fixed sleeve. The two sleeves 14, 17 and the work tube 12 are capable of axial movement along the work spindle it) this movement being imparted by a mechanism "about to be described. This mechanism as viewed in the direction of the axis of the work spindle comprises an H-shaped lever 18 (see Figure 3) the upper extremity of one of the upright limbs 19 thereof being providedwith-a pin 20 which engages a bushing 21 which in its turn engages agroove in the outermost sleeve 17. The lower end of the limb 19 of the H-shaped lever is provided with a roller '22 which engages a groove in a barrel cam 23, arranged to rotate about an axis parallel with the work spindle. A fiat sided slotted bar 24 fixed to the lathe body extends between the two upright limbs 19 and 25 of the H-shaped lever below the cross bar and a pin 26 pivotally carrying a bushing 44 extends through the slot in the bar and is secured between the two upright limbs, the bushing being a slidable fit in the aforesaid slot. 'The outer face of the upright limb 25 of the H-shaped lever is provided with a channel 27 along which slides a block 28 having a hole therein. Overlying the channelled limb is a lever arm 29 mounted to swing about a trunnion 30 disposed intermediate of its ends, which trunnion is accommodated in a bearing 31 in a fixed part of the frame. The lever arm 29 is also provided with a channel 32 in which is slidably mounted a second block 33 having a pin 34 which extends into the hole in the first said block 28. The second block is provided with a threaded hole which is engaged by a lead screw 35 rotatably mounted in a bearing at the upper end of the lever arm 29 and provided with a suitable manipulating handle 36. Thus by rotating the handle the two blocks 28, 33 may be slid along the two channels 27, 32. The aforesaid pin 34 which passes from one block to the other is engaged by the looped end 37 of a tension spring 38 which extends laterally of the two levers and is anchored at its other end 39 to a fixed part of the mechanism thereby tending to hold a boss 40 on the latter lever arm 29 against an adjustable stop 41 mounted on a fixed part of the lathe.

The shaft 42 of the aforesaid cam 23 is driven from the backshaft of the lathe through a one revolution stop clutch of known form.

At the appropriate time for feeding a fresh length of bar through the collet chuck the one revolution stop clutch controlling the cam 23 is engaged causing the cam 23 to revolve once. The cam shaft 42 carries two other cams, one of which 43 first opens the chuck and another of which (not shown) brings a swinging work stop into position in advance of the bar. The cam 23 causes the feed tube 12 and the bar gripped by the fingers to move forwardly until the bar contacts with the swing stop. This offers resistance to further forward travel of the feed tube. Under these conditions the H-shaped lever 18 swings about the bushing 21 at the upper end of the first said upright limb 19 and the blocks 28, 33 which interconnect the other limb 25 with the additional lever arm 29 swing rearwardly against the action of the spring 38 causing the additional lever arm 29 to swing about the trunnion 30. The spring thus provides a cushion against overloading. At this point the chuck closes gripping the bar and further rotation of the cam 23 due to the shaping of the groove therein drags the feed tube and the gripping fingers back over the bar to a position ready for repeating the feeding stroke. The length of the feed stroke, as referred to above is adjusted by rotating the lead screw 35. When the mechanism has fed the bar against the work stop i. e. in the forward position of the feed stroke, the aforesaid H-shaped lever 18 and the additional lever 29 are in alignment with one another, so that irrespective of the length of the stroke the forward position of the feed fingers is always the same. This ensures that the feed fingers always approach the rear end of the chuck and thus make it possible to use the maximum amount of the bar being fed through the machine. Should an obstruction present itself to the forward stroke of the feed tube, before the bar encounters the swing stop, a pivotal movement of the H-shaped lever 18 about the bushing 21 at the top of the first said limb 19 will result causing the spring to be stretched thus preventing a jam-up.

The aforesaid tension spring 38 is so disposed in relation to the channels 27, 32 that as the blocks 28, 33 are moved along the channels towards the aforesaid trunnion 30 the tension in the spring 38 is reduced.

It will be appreciated that as the length of feed is reduced by adjustment of screw 35 the two blocks 28 and 33 move upwards in their respective channels 27, 32. Block 28 provides the fulcrum of the H-shaped lever 18 and takes the thrust when bar feeding. The leverage available for the thrust on the feed tube varies inversely as the feed length is reduced as roller 22 is always swung through the same path by the barrel cam 23 and the effort available on bushing 21 is proportional to the ratio of the distances from block 28 to roller 22 and from block 28 to bushing 21.

As it is not desirable to increase the applied load in the event of an obstruction in the path of the feed tube or bar the load of spring 38 maintaining fulcrum 34 in position is reduced as previously described and thus the thrust on the bar in the event of a stoppage tends to remain constant and the mechanism will always yield at the same load.

I claim:

1. A work feeding mechanism for an automatic lathe comprising a reciprocably work advancing member, a drive shaft, a transmission between the drive shaft and the work advancing member, means for adjusting the transmission whereby the extent of movement imparted to the work may be varied for a given movement of the drive shaft, yielding means in said transmission, a spring restraining said yielding means from yielding, means connecting said adjusting means and the spring, whereby adjustment of the transmission varies the loading on the spring and yielding takes place at substantially the same load on the work irrespective of the variation in the mechanical advantage of the drive shaft over said work advancing member consequent upon the adjustment of the transmission.

2. A work feeding mechanism for an automatic lathe according to claim 1 wherein said spring is a tension spring.

3. A work feeding mechanism for an automatic lathe according to claim 1' wherein said transmission comprises a lever arm mounted to swing about a fixed pivot, a pivot pin adjustable along that lever arm, another lever arm mounted to swing on said adjustable pivot pin, which other lever arm is actuated by the drive shaft and transmits movement to the work, and which spring is arranged to resist swinging movement of the first said lever arm and pivot pin.

4. A work feeding mechanism for an automatic lathe according to claim 1 wherein the transmission comprises a lever arm mounted to swing about a fixed pivot, a second lever arm arranged opposite the first said lever arm and having one end actuated by the drive shaft and the other end connected to the work advancing member, which two lever arms are formed with guideways in two opposed faces thereof, two blocks arranged respectively to slide along the guideways, a pivot pin engaging the said two blocks, means for applying adjusting movement of said blocks pin along the guideway, and a spring arranged to resist swinging movement of the first said lever arm.

5. A work feeding mechanism for an automatic lathe according to claim 1 wherein the transmission comprises a lever arm mounted to swing about a fixed pivot, a second lever arm arranged opposite the first said lever arm and having one end actuated by the drive shaft and the other end connected to the work advancing member, which two lever arms are formed with guideways in two opposed faces thereof, two blocks arranged respectively to slide along the guideways, a pivot pin engaging the said two blocks, means for applying adjusting movement of said blocks along the guideway, and a spring arranged to resist swinging movement of the first said lever arm, which drive shaft includes a barrel cam having a groove therein which is engaged by a cam follower at the end of the lever arm which imparts movement to the work, a projection on said lever arm arranged to engage a guide slot formed in a fixed part of the apparatus parallel with the axis of rotation of the barrel cam, whereby the point of engagement between the lever arm and the barrel cam is prevented from moving transversely to the axis of rotation as the lever arm operates.

References Cited in the file of this patent UNITED STATES PATENTS 1,252,729 Spangler Jan. 8, 1918 1,568,062 Edmond Ian. 5, 1926 1,927,307 Carter Sept. 19, 1933 1,950,931 Rupple Mar. 13, 1934 2,386,706 Moessinger Oct. 9, 1945 2,524,343 Diener Oct. 3, 1950 

